This invention relates to the removal and installation of lawn mower blades, specifically to produce devices to be placed upon or over lawn mower blades to assist in stopping rotation of said blades so they may be safely removed and/or installed.
For peak efficiency, lawn mower blades should be re-sharpened or replaced regularly. It is difficult at best and even dangerous to remove any blade retaining nut or bolt, especially so if the nut or bolt has been over-tightened or rusted in place. The problem is to lock the blade positively against rotation so the high torque necessary to loosen the blade retaining nut or bolt can be applied with a wrench. Holding the blade with a gloved hand does not guarantee enough leverage to loosen the nut especially because blades are routinely installed with a torque tightness of 60 to 120 foot pounds or more and may tend to tighten even more in use.
The typical device to assist users in this procedure that lawn mower manufacturers and their service technicians recommend is a block of wood wedged between the mower housing and the blade. While some commercial mower manufacturers may suggest an impact wrench to remove blades, blades must be re-installed with a hand torque wrench requiring an ability to jam the blade to prevent movement. Using a wood block may result in injury as the block is typically held in place either by gravity or pressure and tends to fall and allow the blade to rotate. This may result in skinned knuckles, cut hands or fingers, or the complete loss of the same. Further, with a mulching deck (which typically is a complete circular tunnel surrounding the blade) there is no place against which the block of wood can be jammed.
Technicians, while performing this process in factory trained shops, commonly use an air wrench to loosen or tighten the blade retaining bolts with one hand while holding the blade with the other. The primary protection for the hands is a rag over the blade or wearing a glove on the hand that holds the blade. This procedure may result in injury to the technician because it depends on their strength and balance to hold the blade steady while using torque of said air wrench. Often, the retaining bolt is frozen or the technician over tightens said retainer and cannot hold the blade. This injury is likely more severe because of the strength and speed of said air tool.
The problem is further compounded by the ground level location of the blade and it is only limitedly visible and accessible through the discharge chute (not present on mulching mowers) unless the mower is elevated using ramps or jacks, tilted backwardly or on its side, or turned upside down. As a practical matter, a heavy riding mower or commercial mower is generally not elevated on blocks just to remove the blades for sharpening. Instead, the mower deck is elevated as far as it will go, which will give about 5″ of visibility and working space for a person lying or crouching on the ground.